Deterioration of trembling aspen clones in the Great Lakes region

Abstract

In order to test the hypothesis that the deterioration of trembling aspen (Populustremuloides Michx.) is related to variations in climate, soil properties, and genotype, 59 trembling aspen clones were sampled in Michigan, Wisconsin, Minnesota, and Ontario. A longevity index (LI) was calculated by taking the difference between predicted basal area from normal yield tables and measured basal area for each clone. Correlations of environmental variables with LI indicate that aspen longevity decreases with increasing mean annual temperature. Under similar temperature regimes, aspen growing on xeric sites and on sites low in exchangeable Ca are most susceptible to early breakup. Since there were negligible differences in soil properties between nine pairs of adjacent deteriorating and relatively well stocked clones, we hypothesize that, under similar environmental conditions, variation in the timing of deterioration may be due to genotypic differences between clones.

Polymorphic site index curves for black spruce and trembling aspen in northwest Ontario

“…Early stand breakup for trembling aspen has been reported for the Great Lakes area (Fralish 1972, Shields andBockheim 1981). The reason for this breakup is increased mortality from white trunk rot and hypoxylon canker (Perala 1977).…”

“…In contrast, poor sites for trembling aspen are shallow to bedrock soils, gravelly morainal soils, coarse-textured sands and poorly-drained mineral and organic soils. On these poor sites aspen growth is slow, yields are small, defects and disease are common and "stand breakup" occurs at relatively young ages (Fralish 1972, Shields and Bockheim 1981, Perala 1991, Carmean 1996.…”

Can forest management based on natural disturbances maintain ecological resilience?

“…A forest that changes as it ages is not necessarily changing states; rather it may be considered to be undergoing compositional and structural change internal to the system without switching to an alternative state, e.g., when a forest changes into a grassland, tundra, or sphagnum bog. However, there are some circumstances when succession may give rise to an alternative and less desired state, such as when a forest undergoes gradual paludification to a bog-like state (Banner et al1983;Fenton et al 2005), or when a shade-intolerant deciduous stand senesces into a permanently shrub-dominated condition (Shields and Bockheim 1981;Nierenberg and Hibbs 2000). In essence, the role played by succession depends on how research questions or management issues are formulated, the time scales involved, and their relationship to relevant system states .…”

Le développement spatial et floristique des populations clonales de peupliers baumier (Populus balsamifera L.) au Nouveau-Québec

“…Les âges maximaux mesurés et estimés lors de la présente étude sont respectivement de 202 et 203 ans. Cette augmentation de la longévité du peuplier en situation marginale a déjà été mentionnée pour les populations de l'Alaska (ROE, 1965) et semble liée à une diminution de la température moyenne annuelle (SHIELDS et BOCKHEIM, 1981 ). La forme de croissance des peupliers de la sous-zone arbustive de la toundra forestière est généralement arbustive et la hauteur maximale atteinte dépend en grande partie du relief local ( fig.…”